I. Field of the Invention
This invention relates to a system, apparatus and method for permanently attaching a coded marker to an article to be identified. More specifically, the invention relates to an optical marker which is digitally coded to represent the part identification number, owner identification number or other information required to be associated with the particular article in question.
II. Description of the Prior Art
As mechanical and electrical systems become more complex, and as theft becomes more of a concern to cost conscious owners, it becomes imperative that a simplified, economical and rapid application marking system be developed in order to identify specific parts either from each other or as to the ownership of a group of parts. It is also strongly desirable that this marking system not be easily visible to the casual observer. Instead the system should be easily visible only to a person with the proper decoding or vision equipment so that quick identification of the part may be established. In this manner the identification marker may be attached to the item in a hidden or nonobvious position which will deter potential pilferage due to the uncertainty as to the fact that the item has been marked or as to the exact location of the marking.
The marking system must be permanent in nature in order that it may not be removed easily from the item. Furthermore the marking system must be inexpensive and easily attached to the item so that the cost of marking each item does not economically outweigh the advantages obtained by having the item marked. The format of the marker must be flexible enough to contain one of a large number of codes, preferably at least one-thousand possible codes, and yet the marker must be very small in order that it may be concealed or hidden from obvious recognition. It is also desirable that the marker contain coded identifications which will require some ambiguous or unknown decoding in order to prevent the untrained observer from identifying the coded information.
The present inventor is unaware of any item or system which will meet the requirements as set forth above. One system which has been examined and discarded as not suitable for application in this regard is the system manufactured and marketed by The Minnesota Mining and Manufacturing Corporation under the trademark MICROTAGGANTS. This system utilizes markers of very small dimensions which are formed by laminating a plurality of color coded plastic sheets together to form a relatively thin plate. The sheets are laminated under pressure with an adhesive in order to form a rigid structure. The edges of this structure are broken or fractured generally at an acute angle with either the top or planar surfaces thereof. The angled edge or side surfaces therefore reveal a sequence of multi-colored layers which may be coded according to color in order to identify a specific lot number, part number or other information of value.
These small markers are approximately the size of a grain of sand and are therefore somewhat difficult to read, normally requiring a one hundred power reading device. Since the colors represent the information contained in the marker, a color coded conversion table must be consulted in order to visually decode the information contained therein. These markers may be suspended in an applicating solution which is attached to the item to be marked or in the alternative may merely be mixed within the substance comprising the items to be identified. For example, this marker has been mixed with gun powder in order to provide positive identification as to the manufacturer and lot number of the explosive. This information provides a method for tracing the subsequent use of explosives and gun powder.
Another marking system which has been examined and discarded as unsuitable is the visual marking systems in which an alpha-numerica code or series of vertically oriented and width modulated lines are read by a visual detection device and digitally decoded in order to represent the alpha-numeric information contained therein. Typically these markers are of substantial size and therefore are unsuitable for satisfying the abovementioned requirements. In addition, expensive detection and decoding equipment is required in order to obtain the information coded upon the marker. Thus, this type of system is not suitable for application to an extremely large number of items to be identified, especially when decoding of the marker must be made in geographically remote or environmentally difficult conditions.
A further marking system which appears to be unsuitable utilizes magnetically encoded marker devices. These systems and devices share the same problems as previously mentioned, mainly that a complex and expensive decoding system must be provided for reading the information contained on the marker. Furthermore, when the magnetic marking systems are exposed to inclement weather and environmentally difficult conditions, the marker may be partially desensitized or demagnetized resulting in the loss of some information. This problem is especially acute when the marker is exposed to extremely cold or hot weather conditions or is exposed to extended periods of irradiation by ultraviolet light. These items and systems are actually subclasses of a larger group of general pattern recognition systems which are oriented towards military applications. While this technology is suitable for the present requirements, the economic expense which would be encountered in implementing such a system on a large scale far outweigh the economic advantages obtained through marking the items.
Previously issued U.S. patents have also been examined in order to determine if a suitable system has been developed by other inventors. For example, Heegaard, in U.S. Pat. No. 3,950,870, discloses a microidentification label having an adhesive backing for coupling to the article to be identified. The label includes an alpha-numeric indicia thereon which is too small to be read by the unaided eye. A plurality of these labels are attached to a master card, and are punched out through the use of a special tool in order to apply them to the article to be marked. A fluorescent agent is added to the adhesive so as to be illuminated with the illumination of black light. While the label is relatively small in size, the indicia upon the label may be easily decoded by an untrained or unauthorized person by the use of a simple magnifying glass. Thus, many of the covert and highly sensitive uses of this label are precluded due to the ease of unauthorized decoding.
Another label having a pressure sensitive adhesive layer on the backside thereof is disclosed by Aoyagi, in U.S. Pat. No. 4,032,679. This label is large and therefore unsuitable for covert uses. Fukuda, in U.S. Pat. No. 3,961,956, discloses a label having an indicia including special printed information which may only be decoded through the use of a matching lenticular lense. While this label will protect from unauthorized decoding the information contained therein, it nevertheless requires a complex and expensive decoder in order to obtain any information from the label.
Various holographic labels have been developed in the prior art. The disclosures of Ward, in U.S. Pat. No. 3,894,756, and Sanders, in U.S. Pat. No. 3,552,853, are typical of the holographically decoded labels. Wilson, in U.S. Pat. No. 3,211,470, discloses a label printed upon paper which is adhesively fastened to the article to be identified. While the digital coding on this label precludes an authorized person from obtaining the information contained thereon, the coded indicia is so complicated that it must be decoded through the use of an expensive and complicated digital machine.
The prior art also reflects various stages of development for applicators designed to apply labels to articles to be identified. Typical examples of these large and bulky label applicators are disclosed by Kronman, in U.S. Pat. No. 2,891,692, Penney, in U.S. Pat. No. 1,812,980, and Putnam, in U.S. Pat. No. 1,648,590. While some of these references employ the use of a sprayable or spreadable adhesive for attaching the label to the article to be identified, none of these references are suitable for modifications which would be required in order to successfully apply microsized labels to the articles to be identified.
The present inventor has examined each of these approaches and in turn has discarded the use of these systems for the reasons as set forth above. Instead the present system concentrates on the basic requirements as previously explained. In order to uniquely identify an article, some unique or repeatable characteristic of the article or marker must be identified and sensed, such as through the use of visual light, x-rays, infrared, ultrasonic, etc. The most economically effective way of establishing such repeatable characteristics is to attach a customized marker to the item to be identified. The use of complicated coding and sensing equipment is discouraged for economic reasons. The use of skilled labor is also discouraged for economic reasons.
One additional problem represented in marking an item is that if a marker is to be attached to an item, it can also be removed surreptitously from the item. In view of these restrictions it becomes apparent that the marker must be attached in some covert manner in order to be completely successful. The marker must be easily coded and decoded and attached to the article in such a manner that it is not readily visible except to an educated observer. In this manner any covert attack upon the article in an attempt to remove the marker must be predicted upon the knowledge of the exact location of the marker on the article. Furthermore, the lack of knowledge as to the exact location of the marker can itself act as a deterrent to the potential theft or illegal use of the article, even if the article is not itself marked.
In view of these limitations the present invention envisions the use of a small microdot marker that is digitally coded in order to be visually decoded with the aid of a sharp eye or a small magnifying glass or microscope.
The problem of coding and decoding has been attacked under the presumption that a large number of the markers must be economically reproduced and attached to an equally large number of items to be marked. The present system envisions the use of high volume photo-reduction techniques for manufacturing the markers. In this manner the coding may be accomplished on a large scale and then reduced to the necessary size. For the sake of economy it is advisable to produce a large sheet of identical codes and then to reduce the entire sheet to usable sizes. This will result in a relatively large number of markers being present upon the same basic master or reproduced item. Empirical experiments have indicated that a marker size of approximately 0.03 inches by 0.03 inches is satisfactory. Digital and alpha-numeric markings on markers of this size are easily readable through the use of a ten-power pocket magnifier or microscope, but in absence of such visual assistance the devices can be read with the naked eye, albeit with some difficulty. Of course, the size of the marker can be varied in order to determine the specific requirements of a particular application.